1 /* $OpenBSD: ssh_api.c,v 1.1 2015/01/19 20:30:23 markus Exp $ */ 2 /* 3 * Copyright (c) 2012 Markus Friedl. All rights reserved. 4 * 5 * Permission to use, copy, modify, and distribute this software for any 6 * purpose with or without fee is hereby granted, provided that the above 7 * copyright notice and this permission notice appear in all copies. 8 * 9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16 */ 17 18 #include "ssh1.h" /* For SSH_MSG_NONE */ 19 #include "ssh_api.h" 20 #include "compat.h" 21 #include "log.h" 22 #include "authfile.h" 23 #include "sshkey.h" 24 #include "misc.h" 25 #include "ssh1.h" 26 #include "ssh2.h" 27 #include "version.h" 28 #include "myproposal.h" 29 #include "ssherr.h" 30 #include "sshbuf.h" 31 32 #include <string.h> 33 34 int _ssh_exchange_banner(struct ssh *); 35 int _ssh_send_banner(struct ssh *, char **); 36 int _ssh_read_banner(struct ssh *, char **); 37 int _ssh_order_hostkeyalgs(struct ssh *); 38 int _ssh_verify_host_key(struct sshkey *, struct ssh *); 39 struct sshkey *_ssh_host_public_key(int, struct ssh *); 40 struct sshkey *_ssh_host_private_key(int, struct ssh *); 41 int _ssh_host_key_sign(struct sshkey *, struct sshkey *, u_char **, 42 size_t *, u_char *, size_t, u_int); 43 44 /* 45 * stubs for the server side implementation of kex. 46 * disable privsep so our stubs will never be called. 47 */ 48 int use_privsep = 0; 49 int mm_sshkey_sign(struct sshkey *, u_char **, u_int *, 50 u_char *, u_int, u_int); 51 DH *mm_choose_dh(int, int, int); 52 53 /* Define these two variables here so that they are part of the library */ 54 u_char *session_id2 = NULL; 55 u_int session_id2_len = 0; 56 57 int 58 mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp, 59 u_char *data, u_int datalen, u_int compat) 60 { 61 return (-1); 62 } 63 64 DH * 65 mm_choose_dh(int min, int nbits, int max) 66 { 67 return (NULL); 68 } 69 70 /* API */ 71 72 int 73 ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params) 74 { 75 char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT }; 76 struct ssh *ssh; 77 char **proposal; 78 static int called; 79 int r; 80 81 if (!called) { 82 OpenSSL_add_all_algorithms(); 83 called = 1; 84 } 85 86 ssh = ssh_packet_set_connection(NULL, -1, -1); 87 if (is_server) 88 ssh_packet_set_server(ssh); 89 90 /* Initialize key exchange */ 91 proposal = kex_params ? kex_params->proposal : myproposal; 92 if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0) { 93 ssh_free(ssh); 94 return r; 95 } 96 ssh->kex->server = is_server; 97 if (is_server) { 98 #ifdef WITH_OPENSSL 99 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server; 100 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server; 101 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 102 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 103 ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_server; 104 #endif /* WITH_OPENSSL */ 105 ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_server; 106 ssh->kex->load_host_public_key=&_ssh_host_public_key; 107 ssh->kex->load_host_private_key=&_ssh_host_private_key; 108 ssh->kex->sign=&_ssh_host_key_sign; 109 } else { 110 #ifdef WITH_OPENSSL 111 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client; 112 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client; 113 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; 114 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; 115 ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_client; 116 #endif /* WITH_OPENSSL */ 117 ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_client; 118 ssh->kex->verify_host_key =&_ssh_verify_host_key; 119 } 120 *sshp = ssh; 121 return 0; 122 } 123 124 void 125 ssh_free(struct ssh *ssh) 126 { 127 struct key_entry *k; 128 129 ssh_packet_close(ssh); 130 /* 131 * we've only created the public keys variants in case we 132 * are a acting as a server. 133 */ 134 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { 135 TAILQ_REMOVE(&ssh->public_keys, k, next); 136 if (ssh->kex && ssh->kex->server) 137 sshkey_free(k->key); 138 free(k); 139 } 140 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { 141 TAILQ_REMOVE(&ssh->private_keys, k, next); 142 free(k); 143 } 144 if (ssh->kex) 145 kex_free(ssh->kex); 146 free(ssh); 147 } 148 149 void 150 ssh_set_app_data(struct ssh *ssh, void *app_data) 151 { 152 ssh->app_data = app_data; 153 } 154 155 void * 156 ssh_get_app_data(struct ssh *ssh) 157 { 158 return ssh->app_data; 159 } 160 161 /* Returns < 0 on error, 0 otherwise */ 162 int 163 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) 164 { 165 struct sshkey *pubkey = NULL; 166 struct key_entry *k = NULL, *k_prv = NULL; 167 int r; 168 169 if (ssh->kex->server) { 170 if ((r = sshkey_from_private(key, &pubkey)) != 0) 171 return r; 172 if ((k = malloc(sizeof(*k))) == NULL || 173 (k_prv = malloc(sizeof(*k_prv))) == NULL) { 174 free(k); 175 sshkey_free(pubkey); 176 return SSH_ERR_ALLOC_FAIL; 177 } 178 k_prv->key = key; 179 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); 180 181 /* add the public key, too */ 182 k->key = pubkey; 183 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 184 r = 0; 185 } else { 186 if ((k = malloc(sizeof(*k))) == NULL) 187 return SSH_ERR_ALLOC_FAIL; 188 k->key = key; 189 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); 190 r = 0; 191 } 192 193 return r; 194 } 195 196 int 197 ssh_set_verify_host_key_callback(struct ssh *ssh, 198 int (*cb)(struct sshkey *, struct ssh *)) 199 { 200 if (cb == NULL || ssh->kex == NULL) 201 return SSH_ERR_INVALID_ARGUMENT; 202 203 ssh->kex->verify_host_key = cb; 204 205 return 0; 206 } 207 208 int 209 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) 210 { 211 return sshbuf_put(ssh_packet_get_input(ssh), data, len); 212 } 213 214 int 215 ssh_packet_next(struct ssh *ssh, u_char *typep) 216 { 217 int r; 218 u_int32_t seqnr; 219 u_char type; 220 221 /* 222 * Try to read a packet. Return SSH_MSG_NONE if no packet or not 223 * enough data. 224 */ 225 *typep = SSH_MSG_NONE; 226 if (ssh->kex->client_version_string == NULL || 227 ssh->kex->server_version_string == NULL) 228 return _ssh_exchange_banner(ssh); 229 /* 230 * If we enough data and a dispatch function then 231 * call the function and get the next packet. 232 * Otherwise return the packet type to the caller so it 233 * can decide how to go on. 234 * 235 * We will only call the dispatch function for: 236 * 20-29 Algorithm negotiation 237 * 30-49 Key exchange method specific (numbers can be reused for 238 * different authentication methods) 239 */ 240 for (;;) { 241 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) 242 return r; 243 if (type > 0 && type < DISPATCH_MAX && 244 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && 245 ssh->dispatch[type] != NULL) { 246 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) 247 return r; 248 } else { 249 *typep = type; 250 return 0; 251 } 252 } 253 } 254 255 const u_char * 256 ssh_packet_payload(struct ssh *ssh, size_t *lenp) 257 { 258 return sshpkt_ptr(ssh, lenp); 259 } 260 261 int 262 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) 263 { 264 int r; 265 266 if ((r = sshpkt_start(ssh, type)) != 0 || 267 (r = sshpkt_put(ssh, data, len)) != 0 || 268 (r = sshpkt_send(ssh)) != 0) 269 return r; 270 return 0; 271 } 272 273 const u_char * 274 ssh_output_ptr(struct ssh *ssh, size_t *len) 275 { 276 struct sshbuf *output = ssh_packet_get_output(ssh); 277 278 *len = sshbuf_len(output); 279 return sshbuf_ptr(output); 280 } 281 282 int 283 ssh_output_consume(struct ssh *ssh, size_t len) 284 { 285 return sshbuf_consume(ssh_packet_get_output(ssh), len); 286 } 287 288 int 289 ssh_output_space(struct ssh *ssh, size_t len) 290 { 291 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); 292 } 293 294 int 295 ssh_input_space(struct ssh *ssh, size_t len) 296 { 297 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); 298 } 299 300 /* Read other side's version identification. */ 301 int 302 _ssh_read_banner(struct ssh *ssh, char **bannerp) 303 { 304 struct sshbuf *input; 305 const char *s; 306 char buf[256], remote_version[256]; /* must be same size! */ 307 const char *mismatch = "Protocol mismatch.\r\n"; 308 int r, remote_major, remote_minor; 309 size_t i, n, j, len; 310 311 *bannerp = NULL; 312 input = ssh_packet_get_input(ssh); 313 len = sshbuf_len(input); 314 s = (const char *)sshbuf_ptr(input); 315 for (j = n = 0;;) { 316 for (i = 0; i < sizeof(buf) - 1; i++) { 317 if (j >= len) 318 return (0); 319 buf[i] = s[j++]; 320 if (buf[i] == '\r') { 321 buf[i] = '\n'; 322 buf[i + 1] = 0; 323 continue; /**XXX wait for \n */ 324 } 325 if (buf[i] == '\n') { 326 buf[i + 1] = 0; 327 break; 328 } 329 } 330 buf[sizeof(buf) - 1] = 0; 331 if (strncmp(buf, "SSH-", 4) == 0) 332 break; 333 debug("ssh_exchange_identification: %s", buf); 334 if (ssh->kex->server || ++n > 65536) { 335 if ((r = sshbuf_put(ssh_packet_get_output(ssh), 336 mismatch, strlen(mismatch))) != 0) 337 return r; 338 return SSH_ERR_NO_PROTOCOL_VERSION; 339 } 340 } 341 if ((r = sshbuf_consume(input, j)) != 0) 342 return r; 343 344 /* 345 * Check that the versions match. In future this might accept 346 * several versions and set appropriate flags to handle them. 347 */ 348 if (sscanf(buf, "SSH-%d.%d-%[^\n]\n", 349 &remote_major, &remote_minor, remote_version) != 3) 350 return SSH_ERR_INVALID_FORMAT; 351 debug("Remote protocol version %d.%d, remote software version %.100s", 352 remote_major, remote_minor, remote_version); 353 354 ssh->compat = compat_datafellows(remote_version); 355 if (remote_major == 1 && remote_minor == 99) { 356 remote_major = 2; 357 remote_minor = 0; 358 } 359 if (remote_major != 2) 360 return SSH_ERR_PROTOCOL_MISMATCH; 361 enable_compat20(); 362 chop(buf); 363 debug("Remote version string %.100s", buf); 364 if ((*bannerp = strdup(buf)) == NULL) 365 return SSH_ERR_ALLOC_FAIL; 366 return 0; 367 } 368 369 /* Send our own protocol version identification. */ 370 int 371 _ssh_send_banner(struct ssh *ssh, char **bannerp) 372 { 373 char buf[256]; 374 int r; 375 376 snprintf(buf, sizeof buf, "SSH-2.0-%.100s\r\n", SSH_VERSION); 377 if ((r = sshbuf_put(ssh_packet_get_output(ssh), buf, strlen(buf))) != 0) 378 return r; 379 chop(buf); 380 debug("Local version string %.100s", buf); 381 if ((*bannerp = strdup(buf)) == NULL) 382 return SSH_ERR_ALLOC_FAIL; 383 return 0; 384 } 385 386 int 387 _ssh_exchange_banner(struct ssh *ssh) 388 { 389 struct kex *kex = ssh->kex; 390 int r; 391 392 /* 393 * if _ssh_read_banner() cannot parse a full version string 394 * it will return NULL and we end up calling it again. 395 */ 396 397 r = 0; 398 if (kex->server) { 399 if (kex->server_version_string == NULL) 400 r = _ssh_send_banner(ssh, &kex->server_version_string); 401 if (r == 0 && 402 kex->server_version_string != NULL && 403 kex->client_version_string == NULL) 404 r = _ssh_read_banner(ssh, &kex->client_version_string); 405 } else { 406 if (kex->server_version_string == NULL) 407 r = _ssh_read_banner(ssh, &kex->server_version_string); 408 if (r == 0 && 409 kex->server_version_string != NULL && 410 kex->client_version_string == NULL) 411 r = _ssh_send_banner(ssh, &kex->client_version_string); 412 } 413 if (r != 0) 414 return r; 415 /* start initial kex as soon as we have exchanged the banners */ 416 if (kex->server_version_string != NULL && 417 kex->client_version_string != NULL) { 418 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || 419 (r = kex_send_kexinit(ssh)) != 0) 420 return r; 421 } 422 return 0; 423 } 424 425 struct sshkey * 426 _ssh_host_public_key(int type, struct ssh *ssh) 427 { 428 struct key_entry *k; 429 430 debug3("%s: need %d", __func__, type); 431 TAILQ_FOREACH(k, &ssh->public_keys, next) { 432 debug3("%s: check %s", __func__, sshkey_type(k->key)); 433 if (k->key->type == type) 434 return (k->key); 435 } 436 return (NULL); 437 } 438 439 struct sshkey * 440 _ssh_host_private_key(int type, struct ssh *ssh) 441 { 442 struct key_entry *k; 443 444 debug3("%s: need %d", __func__, type); 445 TAILQ_FOREACH(k, &ssh->private_keys, next) { 446 debug3("%s: check %s", __func__, sshkey_type(k->key)); 447 if (k->key->type == type) 448 return (k->key); 449 } 450 return (NULL); 451 } 452 453 int 454 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) 455 { 456 struct key_entry *k; 457 458 debug3("%s: need %s", __func__, sshkey_type(hostkey)); 459 TAILQ_FOREACH(k, &ssh->public_keys, next) { 460 debug3("%s: check %s", __func__, sshkey_type(k->key)); 461 if (sshkey_equal_public(hostkey, k->key)) 462 return (0); /* ok */ 463 } 464 return (-1); /* failed */ 465 } 466 467 /* offer hostkey algorithms in kexinit depending on registered keys */ 468 int 469 _ssh_order_hostkeyalgs(struct ssh *ssh) 470 { 471 struct key_entry *k; 472 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; 473 char **proposal; 474 size_t maxlen; 475 int ktype, r; 476 477 /* XXX we de-serialize ssh->kex->my, modify it, and change it */ 478 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) 479 return r; 480 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; 481 if ((oavail = avail = strdup(orig)) == NULL) { 482 r = SSH_ERR_ALLOC_FAIL; 483 goto out; 484 } 485 maxlen = strlen(avail) + 1; 486 if ((replace = calloc(1, maxlen)) == NULL) { 487 r = SSH_ERR_ALLOC_FAIL; 488 goto out; 489 } 490 *replace = '\0'; 491 while ((alg = strsep(&avail, ",")) && *alg != '\0') { 492 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) 493 continue; 494 TAILQ_FOREACH(k, &ssh->public_keys, next) { 495 if (k->key->type == ktype || 496 (sshkey_is_cert(k->key) && k->key->type == 497 sshkey_type_plain(ktype))) { 498 if (*replace != '\0') 499 strlcat(replace, ",", maxlen); 500 strlcat(replace, alg, maxlen); 501 break; 502 } 503 } 504 } 505 if (*replace != '\0') { 506 debug2("%s: orig/%d %s", __func__, ssh->kex->server, orig); 507 debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace); 508 free(orig); 509 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; 510 replace = NULL; /* owned by proposal */ 511 r = kex_prop2buf(ssh->kex->my, proposal); 512 } 513 out: 514 free(oavail); 515 free(replace); 516 kex_prop_free(proposal); 517 return r; 518 } 519 520 int 521 _ssh_host_key_sign(struct sshkey *privkey, struct sshkey *pubkey, 522 u_char **signature, size_t *slen, u_char *data, size_t dlen, u_int compat) 523 { 524 return sshkey_sign(privkey, signature, slen, data, dlen, compat); 525 } 526